I. Field of the Invention
This invention relates to an image processing technique for seaming together a plurality of separate small-area high-resolution sub-images to provide a spatial frequency spectrum of a single large-area high-resolution image substantially without introducing image artifacts (e.g., defects at the sub-image seams of the single image). More particularly, the present invention is directed to such a technique making use of pyramid spatial-frequency spectrum analyzers.
II. Description of the Prior Art
Pyramid spectrum analyzers and synthesizers suitable for use in image processing are known in the art, and are described, by way of examples, in U.S. Pat. No. 4,447,886, issued May 8, 1984 to Meeker; U.S. Pat. No. 4,523,230, issued June 11, 1985 to Carlson, et al; and co-pending allowed U.S. Pat. No. 4,692,806, filed Apr. 4, 1984 by Carlson, et al, and assigned to the same assignee as the present application. This co-pending Carlson, et al. patent application, entitled "Real-Time Hierarchal Pyramid Signal Processing Apparatus," discloses pipeline architecture for performing the Burt Pyramid analyzer and/or synthesizer algorithm on a video signal defining successive television image frames. The Burt Pyramid is described in the article "The Laplacian Pyramid as a Compact Image Code," by Peter J. Burt, et al., IEEE Transactions on Communications, Vol. COM-31, No. 4, 532-540, April 1983.
One use of pyramid processing is in so-called machine vision, which is employed for such purposes as surveillance cameras, robotics, and automated "visual inspection" of manufactured items for defects. In this regard, reference is made to co-pending U.S. Pat. No. 4,692,806, filed Apr. 8, 1986 by Anderson, et al., and assigned to the same assignee as the present application. A programmed implementation of the image-data reduction technique disclosed in the co-pending Anderson, et al. application may be carried out by pyramid processor apparatus disclosed in co-pending U.S. Pat. No. 4,703,514, filed Sept. 16, 1985 by van der Wal and assigned to the same assignee as the present application.
In the past, the images processed by pyramid processors were usually derived from a single television camera. Any television camera is capable of viewing only a given limited field of view with a predetermined maximum resolution. If it is desired to view a larger field with this predetermined maximum resolution, it becomes necessary to employ an array comprised of a plurality of television cameras having overlapping fields of view and then "seam" together separate images, derived respectively from each of these television cameras of the array. Such seams, if noticeable, are image artifacts that degrade a large-area, high-resolution image comprised of a plurality of seamed small-area sub-images derived respectively from the separate television cameras of the array. In the case of machine vision, seam artifacts are a particular problem, since they are capable of producing analysis errors that cannot be tolerated. The pyramid processing technique of the present invention overcomes this problem.